let ojb={
    
'sym':function(a,symbol,b){
        if(symbol=='+'){
          return this.jia(a,b)
        }if(symbol=='-'){
          return this.jian(a,b)
        }if(symbol=='*'){
          return this.chen(a,b)  
        }if(symbol=='/'){
          return this.chu(a,b)
        }
    },

    'jia':function(a,b){
         return a+b;
    },

    'jian':function(a,b){
        return a-b;
   },

   'chen':function(a,b) {
       return a*b
   },

   'chu':function(a,b) {
    return a/b
}


}



module.exports=ojb;